1. Field of the Invention
The present invention relates to a recording medium suitable for use in ink-jet recording. The recording medium, particularly useful as a seal or label for ink-jet recording, has an adhesive layer for sticking on its back surface, permits forming a high-quality image, and is excellent in conveyability into a printer from a stacked state.
2. Related Background Art
An ink-jet recording system is a system in which minute droplets of an ink are ejected by any one of various working principles to be applied to a recording medium such as paper, thereby making a record of images, characters and/or the like. A printer, in which the ink-jet recording system is used, has such features that recording can be conducted at high speed and with a low noise, multi-color images can be formed with ease, printing patterns are very flexible, and particular development and fixing treatments are unnecessary. As a result, the printer is widely used as a recording apparatus of images in various applications including information instruments. The ink-jet recording system has also begun to be used in recording of full-color images. Images formed by a multi-color ink-jet system are comparable in quality with multi-color prints by a plate making system and photoprints by a color photographic system, and such printed images can be obtained at lower cost than the usual multi-color prints and photoprints when the number of copies is small. With the improvement in recordability such as speeding up and high definition of recording, and full-coloring of images in the ink-jet recording system, recording apparatus and recording methods have been improved. Thus, there is a need to improve the quality of the recording media.
In recent years, recording media having a coating layer using an alumina hydrate of a boehmite structure have been proposed, and disclosed in, for example, U.S. Pat. Nos. 4,879,166 and 5,104,730, and Japanese Patent Application Laid-Open Nos. 2-276670, 4-37576 and 5-32037.
The ink-receiving layer containing the alumina hydrate in each of these recording media has the following merits:
(1) a dye in an ink is well fixed to the ink-receiving layer because the alumina hydrate has a positive charge, transparency is good, and an image high in print density and good in coloring can be provided;
(2) problems such as bronzing in an black ink and deterioration of light fastness, which may be caused in some cases by using a silica compound, do not arise: and
(3) the resulting recording medium is preferred to the conventional recording media in points of image quality (particularly, image quality in a full-color image) of an image formed thereon, gloss and application to sheets for OHP.
On the other hand, with the speeding-up of ink-jet recording, there has been a demand for improvement of conveyance performance so as to be adapted to a continuous automatic paper feed mechanism in a recording apparatus (printer) in which a plurality of paper sheets is continuously conveyed.
In ordinary sheet-like recording media, however, the ink-receiving layers and the back surfaces (surface opposite to the ink-receiving layer) are both high in smoothness. Such recording media are easy to adhere to each other because the smooth surfaces are opposed to each other when a plurality of such recording media are stacked in a printer. As a result, a failure in conveyance may occur in some cases. In particular, the frequency thereof tends to increase in an environment high in temperature and humidity.
In the ink-receiving layer containing the alumina hydrate, the surface of the ink-receiving layer is easy to be blemished according to handling thereof. When plural sheets of the recording medium, which has been subjected to a sand blasting treatment at the back surface of a base material as disclosed in Japanese Patent Application Laid-Open No. 8-282089, are stacked in a printer and conveyed one by one, the ink-receiving layers of the recording media may be blemished by sharp irregularities formed by the sand blasting treatment in some cases to markedly deteriorate the image quality of images formed thereon.
Processed films having an adhesive layer are disclosed in, for example, Japanese Patent Application Laid-Open No. 2000-229473, Japanese Utility Model Application Laid-Open Nos. 6-20043, 7-19346 and 8-30, Japanese Patent Application Laid-Open Nos. 7-138541 and 11-323790, etc.
The conventional adhesive processed sheets generally spread are composed of an adhesive sheet formed by evenly coating a surface of a base material with an adhesive, and a release sheet provided on the adhesive-coated smooth surface of the base material. The surface formed by the release sheet is also smooth. Upon use thereof, the release sheet is peeled, and the adhesive sheet is stuck on the surface of an adherend. This operation is often conducted by hand.
Therefore, the conventional adhesive processed sheets have the problem of air entering easily between the sheet and the surface of an adherend. The portion where the air has entered is blistered (projected), and thus a blister occurs on the surface side of the adhesive sheet. In particular, this problem is marked when the size of the adhesive sheet is larger than the palm of the hand.
When the surface of the ink-receiving layer is rubbed with hand or some other means to eliminate the air from the air-entered portion (blister), the ink-receiving layer is blemished, or finger marks are left thereon, so that the image quality of the resulting recorded article may be markedly deteriorated in some cases. When such an operation is excessively conducted, blemishes also tend to occur on the ink-receiving layer containing alumina hydrate.
When the adhesive sheet is stuck on a more or less wrong position, the sheet must be stuck again. However, the adhesive sheet stuck once is difficult to be stuck again in a good state because the adhesive sheet has strong adhesive strength, and so the base material of the adhesive sheet is separated, or the adhesive sheet is wrinkled or folded during its peeling operation. In addition, the quality of the adhesive sheet is lowered.
Since the surface of the release sheet on the side of the adhesive layer is smooth in the ordinary adhesive sheet, the adhesive sheets are easy to adhere to each other, since the smooth surfaces thereof are opposed to each other like the recording media both surfaces of which are smooth when plural adhesive sheets are stacked in a printer, so that a failure in conveyance may occur in some cases. The frequency of this problem also tends to increase in an environment high in temperature and humidity in particular.
It is an object of the present invention to provide a recording medium particularly useful as a seal or label for ink-jet recording, which is excellent in conveyability into a printer from a stacked state and hard to develop surface defects on the surface of its ink-receiving layer during conveyance in the printer and also upon sticking of a recorded article on an adherend after ink-jet recording, and prevents the image quality of an image formed thereon from being impaired.
The present inventors have carried out an extensive investigation with a view toward achieving the above object, thus leading to completion of the present invention. Namely, the above object can be achieved by the present invention described below.
According to the present invention, there is thus provided a recording medium comprising a base material, an ink-receiving layer containing an alumina hydrate provided on one side of the base material, an adhesive layer provided on the side opposite to the ink-receiving layer of the base material, and a release sheet covering the adhesive layer, wherein the surface of the adhesive layer on the side of the release sheet has such structure that recessed portions and projected portions are regularly repeated, and a recessed and projected surface corresponding to the recessed portions and the projected portions of said surface of the adhesive layer is formed by the release sheet covering the adhesive layer.
In the recording medium according to the present invention, the regularly recessed portions and projected portions are formed in the surface (release sheet surface) composed of the release sheet covering the adhesive layer, whereby adhesion between the release sheet surfaces or between the release sheet surface and the ink-receiving layer surface is effectively prevented even when such recording media are stacked, and so the conveyability into a printer from a stacked state is improved. In addition, since the recessed and projected portions are formed in the release sheet surface, the surface does not become a coarse irregular surface, so that even when the release sheet surface comes into contact with the ink-receiving layer surface, the ink-receiving layer is prevented from being blemished. In addition, the irregularities in the release sheet surface are transferred to the adhesive layer surface, and the irregularities are formed in this adhesive layer surface, whereby resticking after the recording medium is stuck once as an adhesive sheet on an adherend can be simply conducted with good operability.